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Fish are expected to shrink in size by 20 to 30 per cent if ocean temperatures continue to climb due to climate change.

A new study by researchers at the University of British Columbia provides a deeper explanation of why fish are expected to decline in size.

Fish are expected to shrink in size by 20 to 30 per cent if ocean temperatures continue to climb due to climate change.

A new study by researchers at the University of British Columbia provides a deeper explanation of why fish are expected to decline in size.

“Fish, as cold-blooded animals, cannot regulate their own body temperatures. When their waters get warmer, their metabolism accelerates and they need more oxygen to sustain their body functions,” said William Cheung, co-author of the study, associate professor at the Institute for the Ocean and Fisheries and director of science for the Nippon Foundation-UBC Nereus Program. “There is a point where the gills cannot supply enough oxygen for a larger body, so the fish just stops growing larger.”

Daniel Pauly, the study’s lead author and principal investigator of the Sea Around Us at the Institute for the Ocean and Fisheries, explains that as fish grow into adulthood their demand for oxygen increases because their body mass becomes larger. However, the surface area of the gills — where oxygen is obtained — does not grow at the same pace as the rest of the body. He calls this set of principles that explains why fish are expected to shrink “gill-oxygen limitation theory.”